The Thermocline and How it Affects Summer Crappie Fishing

Thermocline and effects on fishing

It is a well known fact that Crappie will move to deeper water in the summer.  But deeper water doesn’t necessarily mean that they are all the way at the bottom.

If you are going to be a successful Crappie fisherman in the Summer, particularly in Southern climates, you need to understand the thermocline and how it works.


What is the Thermocline?


The thermocline is the thin layer of water that is sandwiched between the upper layer close to the surface, and the bottom layer.  The bottom layer (also known as the hypolimnion) is usually but not always void of oxygen.  There is very little plant life there due to low sunlight.  Also, things that fall into the lake go to the bottom to decay.

The top layer (also known as the epilimnion) can often be 80 degrees or more in the Summer.  The Epilimnion allows sunlight to penetrate, thereby driving the Crappie deeper.

The Thermocline Is Where Fishing is Just Right

That leaves the thermocline as the “sweet spot”.  This is where the water is not too hot, doesn’t allow too much light penetration, and has enough oxygen for the fish to be comfortable.  Water temperatures in the thermocline may be 10 degrees lower than surface water temperatures.

How to Find the Thermocline

There are different ways to find the thermocline.

The poor boy way of doing it is to drop a meat thermometer down to different levels to find where the temperature changes.

Perhaps a better way to do it is the use of a good depth finder.  You can see a line across your depth finder indicating the change.

Many people believe that the thermocline sets up at around 22″.  If the lake is shallower, it would obviously set up a bit shallower. If the lake is much below 20′ deep, no thermocline will set up.

The thermocline is usually a few feet thick as well.

The water will “turn” in the fall.  As the temperatures drop, the surface water will sink to the bottom, and the bottom will rotate up.

Keep the thermocline in mind on your next Summer Crappie fishing trip, and you’ll have better luck finding your mess of fish.

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